Geography Reference
In-Depth Information
Ordinal icons are very much like nominal icons except that they come in different sizes
that suggest comparable size or order (hence, ordinal ). On some maps, for example, a tiny air-
plane might be used to symbolize a small airport, while a larger airplane is used to indicate
a major airport. Similarly, a lower case u might be used to pinpoint a minor uranium deposit
while a capital U locates a major one.
Dots are often used to show how the distribution of something varies numerically from
place to place. Thus, for example, a map showing the geography of dairy cattle might use a
series of dots, each one representing, say, 100 head of cattle. Similarly, a map of tobacco farm-
ing might use a series of dots, each representing, say, 100 acres of land in cultivation.
Proportional symbols vary in size in direct relation to numerical values. Thus, circles
whose areas are proportional to population may indicate the locations and sizes of cities (Fig-
ure 5-4).
Figure 5-4: This
map uses pro-
portional circles
to indicate the
size of cities.
Line symbols
A number of important features on Earth's surface are linear in nature, meaning they look like lines,
such as roads or railways. Likewise, migration, travel, trade, and other movements of interest to geo-
graphy are basically linear phenomena that connect points. Accordingly, line symbols are common
features on maps and take one of the following forms.
Nominal lines note the locations of particular linear features, such as roads, railways,
rivers, and borders. They may appear as solid, dashed, or embellished lines, the standard sym-
bol for railroads being an example of the latter. Colors may also be employed. Blue lines, for
example, are commonly used to indicate rivers.
Ordinal lines vary in thickness or color to indicate relative importance. On many maps,
for example, city, state, and country boundaries are progressively thicker so as to indicate the
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